1. Field of the Invention
The present invention relates to a data display control apparatus, a data transmission apparatus, and a data display control information editing apparatus. In particular, the present invention relates to a data display control apparatus for controlling the display of a plurality of sets of multimedia data which are linked to one another, a data transmission apparatus for transmitting information controls the display of multimedia data, and to a data display control information editing apparatus for editing information used to control the display of multimedia data.
2. Description of the Related Art
Since the development of digital satellite broadcasting in recent years, there has been a great increase in the number of programs being provided on an ever greater number of channels. For digital satellite broadcasting, large numbers of channels are possible by multiplexing the channels together into a single frequency band. This multiplexing is performed using what is called a "transport stream" under MPEG2 (Moving Pictures Experts Group2) standard. This technique is described in detail in the documentation for ISO/IEC Standard 13818-1 (MPEG2) system standard).
Here, it is possible to conceive a digital broadcasting system where image information and the like are transmitted from a transmission station and received by a receiver terminals, with users of the receiver terminals making interactive operations for the image information in accordance with the content of the transmitted image information.
The above kind of digital broadcasting system is disclosed by a concurrent patent application with the title "Digital Broadcasting System, Digital Broadcasting Apparatus, and Receiver Apparatus for a Digital Broadcast" (Japanese Patent Application No. H9-62216). The characteristic feature of this digital broadcasting system is that it provides a variety of interactive services using only a one-way transfer of data. The system is described in more detail below.
The construction of the digital broadcasting system which is presupposed for the present invention is shown in FIG. 1. This digital broadcasting system is composed of a data transmission apparatus 101 and a plurality of data reception apparatuses 121.
Data Transmission Apparatus 101
The data transmission apparatus 101 is constructed to multiplex data for a plurality of contents, which feature hyperlinks to one another, into an MPEG2 transport stream and to repeatedly transmit the multiplexed data. This data transmission apparatus 101 is composed of a transmission data storage unit 102, and data multiplexing unit 103, a multiplexing information storage unit 104, a system information table generating unit 105, and a transmission unit 106. Here, the term "content" is used to express the unit of information for which interactive operations can be performed by the user.
The transmission data storage unit 102 is composed of a recording medium such as a magnetic disc, and stores data for a plurality of contents which compose one interactive program, and construction information. This transmission data storage unit 102 includes a presentation information storage unit 107, a navigation information storage unit 108, and a construction information storage unit 109. Here, an "interactive program" refers to an "event" or "program" which is included in the MPEG2 transport stream used as the transmission data.
The presentation information storage unit 107 stores presentation information, such as image data and audio data, which is included in each content. The navigation information storage unit 108 stores the navigation information which is composed of hyperlink information for links to other contents, operation control information such as scripts for switching the display, and supplementary display images for displaying menus and the like on a display screen. The construction information storage unit 109, meanwhile, stores a construction information table which shows the correspondence between sets of image data and navigation information.
The multiplexing information storage unit 104 stores a multiplexing information table including identifiers and assigning information for resources such as bandwidth for multiplexing the transmission data stored in the transmission data storage unit 102 into an MPEG2 transport stream.
This multiplexing information table includes packet identifiers (PID) which are assigned to the components that compose each event, when the data stored in the transmission data storage unit 102 is multiplexed into the MPEG2 transport stream as an event.
The components referred to here are streams which are each identified by a PID under IS/IEC 13010-1 (hereinafter, MPEG2 system) standard, with there being video components, audio components, components for multiplexing navigation information, and components for multiplexing stream correspondence information (described later in this specification).
The data multiplexing unit 103 is composed of a multiplexing control unit 110 made up of a CPU and memory, a stream correspondence information table generating unit 111, an identifier information appending unit 112, a navigation information table generating unit 113, and a multiplexing unit 114.
On being activated by the transmission unit 106, the multiplexing control unit 110 first reads the construction information table and the multiplexing information table stored in the construction information storage unit 109 and the multiplexing information storage unit 104, and assigns identifiers for uniquely identifying each content in the digital broadcast for each content number, in doing so generating a content identifier assigning table. After this, the multiplexing control unit 110 assigns values of a "PID", "component_tag", and "stream_id" to each set of image data and generates a display image information identifier assigning table. The multiplexing control unit 110 also instructs the stream correspondence information table generating unit 111 to generate a stream correspondence table, instructs the identifier information appending unit 112 to add the identifier VE.sub.id for image data (video element "VE") to the private area of the image data, and instructs the navigation information table generating unit 113 to generate the navigation information table for the navigation elements "NE".
On being instructed by the multiplexing control unit 110 to add the identifier information, the identifier information appending unit 112 reads the image data stored in the presentation information storage unit 107. The identifier information appending unit 112 then writes the image data identifier VE_id into the private area of the image data bit stream it has read. It should be noted here that the identifier information appending unit 112 obtains the VE_id by referring to the display image information identifier assigning table generated by the multiplexing control unit 110. The identifier information appending unit 112 then assigns a filename to the image data bitstream with the added VE_id information and stores it in a storage area (not illustrated). After appending identifier information to all of the image data, the identifier information appending unit 112 informs the multiplexing control unit 110 of the completion or the appending operation.
On being instructed by the multiplexing control unit 110 to generate a navigation information table, the navigation information table generating unit 113 reads the navigation information stored in the navigation information storage unit 108. When the read navigation information includes hyperlink information, the navigation information table generating unit 113 refers to the content identifier assigning table for information regarding the link destination given as a content number and converts this content number into a variety of identifiers to generate a navigation information table. When no hyperlink information is included, the navigation information table generating unit 113 generates the navigation information table by using the read navigation information as it is, changing only the filename. The navigation information table generating unit 113 stores the generated navigation information table in a storage area (not illustrated). Hereinafter, the expression "navigation information" will mainly refer to the navigation information tables generated here.
On completing the generation of the navigation information tables, the navigation information table generating unit 113 informs the multiplexing control unit 110 of the completion of its processing.
On being instructed by the multiplexing control unit 110 to generate a stream corresponding table, the stream correspondence information table generating unit 111 refers to the display image information identifier assigning table and generates a stream correspondence table for each set of image data. These stream correspondence tables are used by data reception apparatuses to separate one set of image data from the stream transmitted from the data transmission apparatus 101 to the data reception apparatus 121. Hereinafter, the expression "stream correspondence information" will mainly refer to the stream correspondence tables generated here.
On completing the generation of the stream correspondence tables, the stream correspondence information table generating unit 111 informs the multiplexing control unit 110 of the completion of its processing.
On receiving indications for the completion of processing by the identifier information appending unit 112, the navigation information table generating unit 113, and the stream correspondence information table generating unit 111, the multiplexing control unit 110 decides the number of contents which are to be repeatedly transmitted.
The multiplexing unit 114 multiplexes the transmission data into an MPEG2 transport stream.
The system information table generating unit 105 refers to the multiplexing information storage unit 104 and generates the NIT (Network Information Table), the EIT (Event Information Table), the SDT (Service Description Table), the PAT (Program Association Table), and the PMT (Program Map Table). These tables compose the program specification information which is used by the data reception apparatus 121 in selecting a program. Hereinafter, the tables, such as the NIT and EIT, generated by the system information table generating unit 105 will be generally referred to as the "system information".
On being instructed by the multiplexing control unit 110, the system information table generating unit 105 refers to the multiplexing information storage unit 104 and generates the NIT, the EIT, the SDT, and the PAT in accordance with DVB-SI standard and MPEG2 system standard. These tables include information which is required by the data reception apparatus 121 to select the events which are composed of the data stored in the transmission data storage unit 102.
The NIT stores information which relates to the transfer path for each transport stream transmitted from a network identified as the specified network. The EIT stores information, such as event names, starting times, and ending times, for each of the events in a specified service. The SDT stores information, such as service names, for each service included in a specified transport stream.
The PAT includes information for the PIDs of the PMT (Program Map Table) for each program included in a specified transport stream.
The system information table generating unit 105 also refers to the multiplexing information table and generates the PMT. The PMT includes PIDs for identifying each component which composes a program, the types of data transmitted in each component, and information for the descriptors which corresponds to each component.
The transmission unit 106 includes a scheduler, and activates the multiplexing control unit 110 at a predetermined time before the transmission start time of an event, such as five minutes before transmission. When the transmission start time is reached, the transmission unit 106 repeatedly multiplexes information such as the NIT, PAT, PMT, SDT, and EIT generated by the system information table generating unit 105 into the transport stream outputted by the multiplexing unit 114 at a predetermined interval using predetermined PIDS in accordance with DVB-SI standard and MPEG2 system standard. The transmission unit 106 then performs modulation and other processes, before transmitting the data to a plurality of data reception apparatuses 121.
As described above, the data transmission apparatus 101 assigns identifiers to the image data and navigation information table which compose each content, multiplexes them into a transport stream, and repeatedly performs transmission.
The navigation information includes identifiers of a set of image data and a set of navigation information in the content linked by a hyperlink, as well as supplementary image information for displaying menus and the like, and scripts for switching the display. As a result, the data reception apparatus 121 can freely separate and reproduce a content from the transport stream by specifying the identifiers in accordance with the navigation information, which means that interactive operations can be performed for data transmitted using a one-way communication path.
Data Reception Apparatus
The data reception apparatus 121 is constructed to selectively obtain and reproduce a content from the MPEG2 transport stream transmitted by the data transmission apparatus 101, in accordance with an interactive operation made by the user. This data reception apparatus 121 is composed of a reception unit 122, a TS decoder unit 123, an AV decoder unit 124, a received data storage unit 125, a reception control unit 126, a signal reception unit 127, a reproduction unit 128, a display unit 129, and an audio output unit 130.
The reception unit 122 receives the MPEG2 transport stream which corresponds to the transport stream identifier indicated by the reception control unit 126, and outputs it to the TS decoder unit 123.
The TS decoder unit (transport decoder unit) 123 includes a filter condition storage unit 131 for storing the filter conditions set by the reception control unit 126, and operates in accordance with these filter conditions so as to only separate image data or audio data with a specified identifier from the transport stream outputted by the reception unit 122. The TS decoder unit 123 outputs the separated data to the AV decoder unit 124. The TS decoder unit 123 also separates stream correspondence tables, navigation information tables, and system information tables which have been multiplexed as table data under MPEG2 standard, and outputs the table data to areas maintained in the received data storage unit 125, in accordance with the identifiers.
The TS decoder unit 123 also separates the PCR (Program Clock Reference) with the specified identifier and outputs it to the AV decoder unit 124. It should be noted here that the filter condition storage unit 131 can simultaneously store a plurality of filter conditions and that the TS decoder unit 123 can simultaneously perform a plurality of separation operations in parallel.
The AV decoder unit 124 includes a clock unit which is not illustrated. This clock unit is synchronized to a standard time using the value of the PCR outputted by the TS decoder unit 123, and is used to measure time which is used as the standard for synchronized decoding of image data and audio data.
On receiving image data and/or audio data from the TS decoder unit 123, the AV decoder unit 124 reads the identifier of the image data and/or audio data written in the private are, in accordance with an indication from the reception control unit 126, and notifies the reception control unit 126 of the identifier(s). Next, the AV decoder unit 124 decodes the image data and/or audio data in predetermined units in accordance with an indication from the reception control unit 126 and outputs the decoded data to the reproduction unit 128 in synchronization with the clock unit, before informing the reception control unit 126 of the completion of the decoding.
The received data storage unit 125 can be composed of RAM (Random Access Memory), for example, and is provided with a stream corresponding information table storage unit 132, a navigation information table storage unit 133, and a system information table storage unit 134.
The stream correspondence information table storage unit 132 stores stream correspondence tables which have been separated by the TS decoder unit 123. The navigation information table storage unit 133 stores navigation information tables which have been separated by the TS decoder unit 123. The system information table storage unit 134 stores the system information tables, such as the NIT, the SDT, the EIT, the PAT, and the PMT, which have been separated by the TS decoder unit 123.
The signal reception unit 127 receives signals, such as remote controller operations made by a user, and informs the reception control unit 126 of the received signals.
The reproduction unit 128 superimposes graphics information included in the navigation information table outputted from the reception control unit 126 and image data decoded by the AV decoder unit 124 in accordance with indications from the reception control unit 126. The reproduction unit 128 outputs this combined image to the display unit 129. The reproduction unit 128 also outputs audio data decoded by the AV decoder unit 124 to the audio output unit 130.
The display unit 129 can be realized by a CRT (Cathode Ray Tube) or liquid crystal display, and is used to display the images outputted by the reproduction unit 128.
The audio output unit 130 can be realized by a speaker, and is used to output the audio signal outputted by the reproduction unit 128.
The reception control unit 126 is composed of a CPU and a program for controlling the CPU. The reception control unit 126 controls the reception unit 122 and has it receive a desired transport stream. On receiving a user operation signal via the signal reception unit 127, the reception control unit 126 refers to the navigation information table presently stored in the navigation information table storage unit 133 and sets the filter condition for the next navigation information table and the filter condition for the stream correspondence table for obtaining the image data in the filter condition storage unit 131 of the TS decoder unit 123. The reception control unit 126 then refers to the stream correspondence table which has been newly separated by the TS decoder unit 123 and stored in the stream correspondence information table storage unit 132, and sets the filter condition for the image data in the filter condition storage unit 131.
The reception control unit 126 judges whether the image data which has been separated by the reception control unit 126 is the appropriate image data by referring to the image data identifier written into the private area of the image data. When the image data is the appropriate image data, the reception control unit 126 has the image data decoded and outputted to the reproduction unit 128. When the image data is not the appropriate image data, the reception control unit 126 changes the filter condition in the filter condition storage unit 131 and gives another indication for the separation of a stream correspondence table.
The reception control unit 126 also reads graphics data for objects included in the supplementary image information in the navigation information table separated by the TS decoder unit 123. The reception control unit 126 also informs the reproduction unit 128 of this data and has the reproduction unit 128 combine the bitmap data with the image data.
As described above, the data reception apparatus 121 can separate the presentation information and navigation information for a specified content from the transport stream when necessary. By doing so, suitable link destination contents can be reproduced in accordance with user operations, so that interactive programs that can be changed in accordance with user operations can be achieved despite the communication being limited to a one-way broadcast from the data transmission apparatus.
Operation
The following is an explanation of the data composition of contents and of the operation for the display of contents by the data reception apparatus 121 in this digital broadcasting system, with reference to the drawings.
FIG. 2 shows an example display which is displayed by the data reception apparatus 121 in the digital broadcasting system described above. This figure shows an example of a mail order program, with there being a content 210 showing a mail order menu, a content 220 introducing video equipment, and a content 230 introducing stereo equipment. Here, switching between these contents can be performed according to user operations, as shown by the arrows 240, 241, 242, and 243.
When the content 210 showing the mail order menu is displayed on the display screen and the user selects and activates the "Video" button 211, the display switches, as shown by arrow 240, from content 210 to a display of content 220 that introduces video equipment. Following this, if the user selects and activates the "Menu" button 221, the display switches back to the content 210 showing the mail order menu, as shown by the arrow 241.
In the same way, when the content 210 showing the mail order menu is displayed on the display screen and the user selects and activates the "Stereo" button 212, the display switches, as shown by arrow 243, from content 210 to a display of content 230. Following this, if the user selects and activates the "Menu" button 231, the display switches back to the content 210 showing the mail order menu, as shown by the arrow 242. Here, buttons 211, 212, 221, and 231 are provided in contents 210, 220, and 230 to allow switches of display in accordance with the interactive operations made by the user.
To achieve the switches of display in response to interactive operations described above, the data which composes each of the contents transmitted by the data transmission apparatus 101 needs to have the construction described below.
FIG. 3 is a simplified representation of the data transmitted by the data transmission apparatus. Here, the transmitted data 201 is composed of data representing the various contents, and is repeatedly transmitted in its entirety, with each repeated transmission having a predetermined time period. This data is repeatedly transmitted to allow the data corresponding to a content selected by an indication of a link destination given by the user to be obtained at any given time. Since the data for the contents is repeatedly transmitted, the user will soon be able to obtain the data for the required content even when the user has commenced viewing midway through the broadcast of the program.
The transmitted data 201 is composed of a plurality of sets of image data 215, 225, and 235, and a plurality of sets of navigation information 216, 226, and 236 which correspond to the sets of image data. These sets of image data 215, 225, and 235 correspond to the background images of contents 210, 220, and 230 which are displayed on the display screen of the data reception apparatus 121.
The sets of navigation information 216, 226, and 236 include bitmap data for on-screen display graphics, such as buttons, which are displayed superimposed onto the sets of image data 215, 225, and 235, scripts which describe operation processes corresponding to user operations, and hyperlinks showing contents that are link destinations for display switching of contents. This hyperlink information is composed of identifiers for the data, such as image data, and the navigation information which compose the link destination contents.
The content 210 shown in FIG. 2 is achieved by the image data 215 and the navigation information 216. In the same way, content 220 shown in FIG. 2 is achieved by the image data 225 and the navigation information 226, and content 230 shown in FIG. 2 is achieved by the image data 235 and the navigation information 236.
FIG. 4 is a model representation of the repeated transmission of data 201 with the given interval. This data 201 is repeatedly transmitted with the given interval by the data transmission apparatus 101.
It should be noted that while the image data and navigation information in FIG. 4 have been illustrated with a frame construction, the respective data is in fact digitized, with image data and corresponding navigation information being multiplexed together and the data 201 being transmitted as an MPEG2 transport stream.
The following is a detailed explanation of the data multiplexed and transmitted by the data transmission apparatus 101.
FIG. 5 shows how the data transmitted by the data transmission apparatus 101 is multiplexed together. As shown in the figure, image data VE (N), navigation information tables NE (N), stream correspondence tables VET (N), and system information such as the PCR, PAT, and PMT are multiplexed together. The arrow 202 in FIG. 5 shows the range of the data 201 in FIG. 4 which is repeatedly transmitted.
In the example shown in FIG. 5, sixty-three contents are multiplexed together, with the sets of image data VE (0) to VE (62) each being multiplexed with the value "0.times.0084" as their PID and a value which is cyclically incremented between "0.times.e0" and "0.times.e.+-." as their stream_id. Each set of stream correspondence information VET (N) is multiplexed with the value "0.times.0083" as their PID and a value equal to the image data identified VE_id as their table_id_extension. Here, one set of stream correspondence information VET (N) is multiplexed for each set of image data VE (N). The sixty-three sets of navigation information NE (0) to NE (62) are multiplexed having been given the value "0.times.0082" as their PID and a value equal to the navigation element identifier NE_id as their table_id13 extension. Here, the PCR, PAT, and PMT are also multiplexed with predetermined values of the PID.
Here, the table_id_extension and stream_id are identifiers which are used in conjunction with the PID to identify the various sets of data.
With the stated data construction, the data reception apparatus 121 can set these identifiers into the filter condition storage unit 131 as indicated by the received data, so that the TS decoder unit 123 can separate the desired data from the transmitted transport stream.
Since the VE.sub.--id identifier of the image data and the NE_id identifier of the navigation information are given in the hyperlink information in the navigation information corresponding to the content presently being displayed to enable the execution of hyperlinks in accordance with user operations, it is possible to separate the data composing the next content to be displayed based on the hyperlink information and so display the next content. This procedure is described in more detail below.
First, the data reception apparatus 121 obtains the PAT of the transponder (satellite broadcasting unit) presently being received. Here, when the program selected by the user is on a different transponder, the data reception apparatus 121 obtains the NIT, refers to the NIT, and controls the reception unit 122 to change the received transponder, although such case will not be described here.
Since the PID of the PAT is set beforehand at "0", the data reception apparatus 121 sets "PID=0" into the filter condition storage unit 131 so as to separate the PAT. Since the PID of the PMT is given in the PAT, the data reception apparatus 121 can obtain the PID of the PMT corresponding to the program and, by setting this into the filter condition storage unit 131, separate the PMT.
The PIDs corresponding to the components are given in the PMT, so that the data reception apparatus 121 can obtain the PID of the stream correspondence table VET, and, by setting the VE_id obtained from the hyperlink information together with the table_id_extension into the filter condition storage unit 131, the stream correspondence table VET corresponding to the desired image data can by obtained.
The component_tag and stream_id are given in the stream correspondence table VET, so that the data reception apparatus 121 can refer to the PMT based on the component_tag and obtain the PID of the appropriate component. By setting this PID and the stream_id in the filter condition storage unit 131, the data reception apparatus 121 can obtain and display the desired image data.
The data reception apparatus 121 is also able to obtain the PID of the component used for multiplexing the navigation information by referring to the PMT, and by setting the NE_id obtained from the hyperlink information with the table_id.sub.13 extension in the filter condition storage unit 131, can separate the desired navigation information.
As a result of the described procedure, the data reception apparatus 121 can obtain the image data and navigation information which compose the new content.
The following is a more detailed explanation of the data construction of the navigation information, using the example of the navigation information 216 which is given in outline in FIG. 3. The data construction of this navigation information 216 is shown in FIG. 6.
The navigation information 216 includes a Bytecode Part 301, a Handler_Part 302, a Graphics_Property_Part 303, a Bitmap_Information_Part 304, and a Hyperlink Information_Part 305.
The Bytecode_Part 301 is equivalent to the part of FIG. 3 represented by the word "Script", and is used to record bytecodes which are one kind of script. These bytecodes include an instruction set, such as conditional branches, integer calculations, and access to constants/variables, which allows basic programming, and to a variety of instruction sets that are related to the control or image and audio data.
In the example in FIG. 6, the bytecode with bytecode number "0" is "Push L0, GotoPage". Here, "Push L0" is an instruction which represents the storing of the value "0" in the stack, while "GotoPage" is an instruction indicating a switch of display to the content shown by the link number whose value is stored in the stack. Here, the link number is given in the Hyperlink Information_Part 305, and is an identifier for identifying a content to be switched to. Accordingly, the bytecode with the bytecode number "0" describes an operation switching the display to the link destination content given by link number "0". In the same way, the bytecode with the bytecode number "1" describes an operation switching the display to the link destination content given by link number "1".
The Handler_Part 302 is used to record the correspondence between handler numbers and bytecode numbers. In the example in FIG. 6, the handler numbers 0 and 1 respectively correspond to the bytecode numbers 0 and 1. It should be noted here that not only bytecodes, but also information defining the processing environment of handlers, such as variable areas, is given corresponding to the handlers.
The Bitmap_Information_Part 304 is the part used to record the content of the bitmaps which display buttons corresponding to the graphics numbers. In the example in FIG. 6, the graphics with the number "0" represent the bitmap "Video", while the graphics with the number "1" represent the bitmap "Stereo".
The Graphics_Property_Part 303 is information for composing the on-screen display graphics to be displayed superimposed onto the video data on the display screen, and so includes graphics numbers for identifying sets of graphics, graphics types, display coordinates for sets of graphics, a handler number associated with the graphics, and an entry showing the initial state for when the content is displayed. For the example in FIG. 6, the type for each set of graphics is "button", with graphics numbers 0 and 1 corresponding to the graphics in the Bitmap_Information_Part 304 with the same values "0" and "1". Hereinafter, the button with the graphics number "n" will be referred to as "button n" or the "nth button". In the present example, button 0 and button 1 are displayed with the x and y coordinates given as (20, 20) and (20, 60), with the handler numbers of the handlers which are activated on selection of the buttons 0 and 1 being "0" and "1". Also, the initial state of button 0 and button 1 when the content is displayed is "visible".
The Hyperlink_Information_Part 305 is used to record the IDs of the materials which compose the link destination contents. This Hyperlink_Information_Part 305 records the IDs as the information showing all of the link destination contents of the content which includes this navigation information. Here, link numbers are given to identify the sets of identifiers for the link destinations of each content. For the example in FIG. 6, NE_id=1, VE_id-1 are recorded for the link destination with the link number "0", with this indicating a link destination content composed of the information in the NE with the ID number "1" and the VE with the ID number "1". The NE_id=2, VE_id=2 are recorded for the link destination with the link number "1", with this indicating a link destination content composed of the information in the NE with the ID number "2" and the VE with the ID number "2".
It should be noted here that NE_id given as "0" at the top of FIG. 6 shows that the navigation information being explained here is the navigation element which has the ID "0".
In the data reception apparatus 121, the reception control unit 126 refers to the navigation information composed of the data described above and displays the button "video" and the button "Stereo" shown in content 210 of FIG. 2. When these buttons are selected and activated by the user, control is performed to switch the display to another content.
When a content is displayed, the reception control unit 126 refers to the Graphics_Property_Part and displays the graphics in order starting from the graphics with the graphics number "0" in the indicated initial state at the indicated coordinates. When a button is selected and activated by the user, the reception control unit 126 executes the handler process corresponding to the handler number given in the Graphics_Property_Part. This handler processing is performed by the reception control unit 126 referring to the Handler_Part and executing the bytecode in the Bytecode_Part which has the bytecode number given corresponding to the handler number in the Handler_Part. It should be noted that this execution of bytecodes is achieved by a bytecode interpreter (not illustrated) in the reception control unit 126 separating and executing one instruction at a time.
In the digital broadcasting system described above, the data, such as the image data and navigation information, necessary for displaying such content is repeatedly multiplexed and transmitted by the data transmission apparatus. The data reception apparatus which receives this data is able to separate data form the transmitted data in accordance with selection and activation operations made by the user, so that a desired content can be displayed. By doing so, an interactive service can be achieved using a one-directional broadcast.
In current broadcasting, there are cases where a broadcast of a same program is repeated several days later, and to reduce production cost and effort, there are demands for the data used to compose a program to be used once again in exactly the same form.
When considering the above demands, a broadcast which includes image data with a content such as "Campaign valid until Sep. 10, 1996" may be broadcast as it is until Sep. 10, 1996. When Sep. 11, 1996 is reached, however, it becomes unsuitable to broadcast the data as it is. In this way, there can be cases where a program will contain data which is not suitable for a repeat broadcast, so that it is necessary to develop a system where control is perform in accordance with the time of broadcast to prevent links to data unsuitable for repeat broadcasting being activated.
It is also common in the world of broadcasting for a variety of different programs to be broadcast at different times, so that there are demands for the dynamic setting of links between programs with different broadcasting times to as to link the various programs. In order to satisfy these demands, it is necessary to have a construction which performs control in accordance with the ending times of programs which are link destinations.
In the above digital broadcasting system, it is necessary to have a control structure for programs which include a time element. By doing so, program producers can efficiently generate and broadcast a great variety of programs, with the viewers being able to enjoy a wider variety of interactive programs.
In order to satisfy the need for the above kind of program service, it is necessary to perform program control with a time element for the system described here as the related art.